The heat generated by an internal combustion engine is generally so great that a special cooling system must be provided to remove heat from the engine in a positive manner and transport it to a reservoir capable of absorbing the excess heat, usually the atmosphere. A commonly employed cooling system uses internal engine conduits through which a liquid coolant circulates under the control of a suitable pump and suitable control valve. The liquid coolant is passed through a radiator generally subjected to selective air flow in which the heat exchange with the atmosphere occurs. Customarily, the coolant is water to which an anti-freeze compound is added in the winter season. Common anti-freeze substances are water-soluble fluids, usually glycol compounds, for example ethylene glycol which may have a number of additives to prevent corrosion, foam formation and to close off minor leaks in the system. The temperature at which the mixture solidifies depends on the ratio of anti-freeze compound to the amount of water present. When an engine is started from the cold state, it is generally desired to attain the operating temperature as rapidly as possible, because only at the correct engine temperature is it feasible to conform to the various optimum conditions of operation, for example the minimum exhaust gas toxicity, minimum fuel consumption, minimum wear and tear, etc. Accordingly, it is desired to make the starting and warm-up phase of the engine operation as short as possible. To accomplish this objective, the water coolant flow is controlled in such a way as to prevent coolant circulation until such time as the engine is sufficiently heated. The coolant flow is usually regulated by thermostatic control valves.
In order to shorten the time required for engine warm-up, it has previously been proposed to preheat parts or all of the engine. However, such preheating requires the expenditure of large amounts of energy and substantial preheating times and is thus highly uneconomical.